Today Myrddyn Phillips of MappingMountain.blogspot.com measured the street to back up 72-year-old Mr Headley's claim.

Mr Phillips work usually involves mapping hills and mountains, but today he used a sophisticated sat nav style device to survey the street, which is accurate to 10cm. This is the first time he has ever mapped a road.

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Mr Headley said: "According to information at its maximum, the slope of Baldwin Street is about 1:2.86 (19° or 35%). But on Wikipedia Llech, or Ffordd Pen Llech is measured with a gradient at its steepest section of 1:2.73, or 36.3%.

"1:2.73 is steeper than 1:2.86 and 36.63% is steeper than 35%.

Ffordd Pen Llech in Harlech which is bidding to be the steepest street in the world (Image: Daily Post Wales)

"We will have to wait a few weeks for the data to come back - it has to be qualified by a mathematician - but if it says what I think to be the case, then we will send that to Guinness to be verified - that could take up to 12 weeks.

"In my mind I am confident, but we will have to wait and see. We are on tenter hooks."

Baldwin Street, Dunedin, New Zealand, which currently holds the title of world's steepest residential street (Image: Google)

Mr Phillips said: "I have taken about 1,500 readings over the last five years, but this is the first time I have surveyed a street and will probably be the steepest street I ever do."

Guinness World Records rates the steepness of a street or road on its maximum gradient rise over a 10 metre span. It must also be available for public and vehicle use.